One of the earliest operations required in the history of automobile assembly was the joining of an inner panel to an outer panel to form any of a variety of body parts, including doors, engine hoods, fuel tank doors and trunk lids, all referred to as “swing panels” which enclose an opening in the vehicle body. Known machines for the forming and joining of sheet materials include the press-and-die set, and the tabletop and roller-forming tool, the latter being the most-recently introduced device.
An unfortunate feature of joining materials is that the sheets tend to become misaligned with each other before or during the joining operation, in part due to the lateral forces applied to the panels during the hemming operation. Certain efforts have been undertaken to overcome this problem.
One known effort employed to prevent the skidding of one sheet relative to the other has been to apply an upper pressure ring from above the sheet materials, thereby pinching the upper and lower sheets between the upper pressure ring and the lower nest member. This practice leads to the consumption of much of the workspace above the sheet materials. In addition, the use of the upper pressure ring requires a high-powered overhead device to effect operation. All considered, the use of the upper pressure ring is costly, inefficient and inconvenient.
An additional known practice to prevent skidding of two sheets during joining is to align the two sheets relative to one another from the side using side gauges. This operation, while offering certain advantages over the use of the upper pressure ring in terms of cost, space and equipment, does a poor job of controlling movement of the sheet materials. Fixture in the form of clamps around the perimeter of the panels ring also be employed to secure the panels. The use of gauges and clamps also leads to defacing of the sheet material through scratching during loading and unloading of the sheet material. Importantly, during operation, the gauges interfere with the travel of the forming tool. In some instances, if the gauges are spring-loaded, the rolling tool may be shocked and may suffer a pressure bounce when struck.
An additional practice has been to simply position one sheet above the other without holding, this latter approach clearly being the least desirable.
Prior approaches to the problem of forming and joining two sheet materials together while restricting movement of the sheets relative to one another had failed. While improving the state of the art, the method and apparatus of co-pending application Ser. No. 10/521,652 to Campian still had remnant sheet material movement. Moreover, even with that improvement, the manufacturing and precise positioning of the vacuum chamber(s) is complex and repair difficult.
Accordingly, prior approaches to solving the problem of providing a method and apparatus for forming and joining two sheet materials together while restricting movement of the sheets relative to one another have failed to overcome the problem.